Ion implantation is a technique for introducing conductivity-altering impurities into semiconductor workpieces. During ion implantation, an intended impurity material is ionized in an ion source chamber, the ions are accelerated to form an ion beam of prescribed energy, and the ion beam is focused and directed toward the surface of a workpiece positioned in a vacuum enclosure. The energetic ions in the ion beam penetrate into the bulk of the workpiece material and are embedded into the crystalline lattice of the material to form a region of intended conductivity.
Semiconductor work pieces are highly susceptible to particulate contamination that can detrimentally alter the conductivity characteristics of a workpiece. In order to mitigate such contamination, ion implantation is typically performed in high vacuum pressure environments. It is therefore beneficial to employ transfer devices for moving workpieces into and out of such vacuum environments in an expeditious manner, while simultaneously minimizing the creation and transmission of particulate matter.
A typical architecture for dealing with two or more processes for a workpiece consists of a mainframe, which provides the mechanisms for handling the workpiece from one process environment to the other. The mainframe can consist of a vacuum chamber, one or more isolation valves (e.g., depending on the number of individual process facets), a workpiece handling robot, and a vacuum system. The mainframe is often the location in which the vacuum level is adjusted to suit varying process operations, depending upon which process the workpiece is being prepared for. As will be appreciated, adjusting the vacuum level in the mainframe is time consuming and employs large, expensive pumps due to the relatively large volume of the mainframe chamber.